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Financing: Long-term Debt (Additional Information) (Details) - USD ($) $ in Millions			9 Months Ended
	Aug. 23, 2024	May 16, 2024	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Repayment of long term debt			$ 600.0	$ 0.0
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] | Senior Unsecured Notes Due 2035 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		$ 450.0
Stated interest rate (percent)		6.00%
Less unamortized deferred financing costs		$ 5.2
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] | Senior Unsecured Notes Due 2024 [Member]
Debt Instrument [Line Items]
Stated interest rate (percent)	1.04%
Repayment of long term debt	$ 600.0

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